1. Field of the Invention
The present invention relates to a needle selector for use in knitting machines such as circular knitting machines and weft knitting machines, and more particularly to a needle selector for use in knitting machines in which knitting needles are selected by a piezoelectric drive mechanism.
2. Description of the Related Art
In a knitting machine such as a circular knitting machine or a weft knitting machine, vertical motions of the knitting needle are selected in accordance with a knitting procedure stored in a recording medium, such as a floppy disk or the like, to knit a fabric of the desired texture. Various needle selectors are used for selecting that vertical motions of the knitting needle.
Before describing the needle selector according to the present invention, an outline of needle selection in a knitting machine will be explained with reference to a circular knitting machine schematically illustrated in FIGS. 6A through 6C.
FIG. 6A shows a schematic perspective view of the basic knitting mechanism of a circular knitting machine. As illustrated in FIG. 6A, in the circular knitting machine, knitting needles 2 are arranged slidably in a plurality of vertical grooves (not shown) around the circumference of a knitting cylinder 1, rotating in the direction indicated by an arrow A, the grooves being provided along the lengthwise axis of the knitting cylinder 1. Underneath the knitting needles 2 are usually disposed needle selection jacks 12 to permit contact with the lower parts of the knitting needles 2. On the other hand, underneath the knitting cylinder 1 is statically arranged a cylindrical cam base 15a, and on the upper part of that cam base are disposed a plurality of cams 15 of a prescribed shape at prescribed intervals.
The basic principle of knitting is such that each of the knitting needles 2 on the rotating knitting cylinder 1 is thrust upward via the needle selection jack 12; a yarn loop is made by feeding yarn 5, taken up from a yarn bobbin 6 into the hooks of a knitting needle 2 projecting from the upper face of the knitting cylinder 1, as a result; and one stitch is formed by lowering the knitting needle 2 with a known mechanism (not shown). Therefore, a desired fabric can be knit by opting either to give a vertical motion to each knitting needle 2 or to allow advancing to the next step of knitting without forming a stitch. In order to provide such motions to knitting needles, in a knitting machine, needle selection jacks 12 are usually arranged underneath and in contact with knitting needles 2, and the vertical motions of the knitting needles are controlled by using a needle selector 3, operating on the basis of information from a controller 4 with a built-in knit texture memory device, to selectively engage the needle selection jacks 12 with the knitting needles 2.
Next will be described with reference to FIGS. 6B and 6C, illustrating the relationship between the selection jacks and the needle selecting means, an instance in which piezoelectric bodies, which are used according to the present invention, are used as means of knitting needle selection.
A piezoelectric body 47 can be either bent in the way shown in FIG. 6B or in the way shown in FIG. 6C, reverse to the bend illustrated in FIG. 6B, depending on how a voltage is applied. At the tip of the piezoelectric body 47 is arranged a finger 9 linked to it. In FIGS. 6B and 6C, the piezoelectric body 47, the finger 9 and a raising cam 15 are positioned within the frame of a drawing, and the knitting needles 2 and the needle selection jacks 12 move circularly together with the knitting cylinder 1 (not shown) from the top to the bottom of the frame of the drawing (or in the reverse direction). The needle selection jacks 12 can swing pivoting on fulcrums 12a, and in the upper part are provided needle selection butts 13 and raising cam butts 14 projecting sideways from the needle selection jacks 12 as illustrated.
When the piezoelectric body 47 is curved as shown in FIG. 6B, the needle selection butts 13 of the needle selection jacks 12, which circularly move, hit the finger 9, and the resultant thrusting of the needle selection jacks 12 in the clockwise direction, pivoting on the fulcrums 12a, prevents the raising cam butts 14 from engaging with the raising cam 15 of the needle selection jacks 12. Therefore, the needle selection jacks 12 fail to be thrust upward by the raising cam 15, and at the same time the knitting needles 2 fail to be thrust upward.
When the piezoelectric body 47 is curved as shown in FIG. 6C, the finger 9 at the tip of the piezoelectric body 47 does not hit the needle selection butts 13 of the needle selection jacks 12 which circularly move together with the knitting cylinder 1, and the needle selection jacks 12 remain in the vertical direction with the result that the raising cam butts 14 at the lower ends of the needle selection jacks 12 are thrust upward along the inclined face of the raising cam 15, the knitting needles 2 being thrust upward along with the thrust.
Selective engagement of the needle selection butts 13 of the needle selection jacks 12 with the finger 9 at the tip of the piezoelectric body 47 enables the knitting needles 2 to move upward freely as desired and thereby enables a knit fabric of any desired texture to be knit.
The single most important performance feature for knitting is high productivity, i.e. the possibility to rotate the knitting cylinder faster. In order to turn the knitting cylinder faster, it is necessary to enable the needle selector for controlling upward shifting of the knitting needles to operate faster. For this reason, various fast operating knitting needle selectors have been developed and came into use.
For instance, the same applicant as that for patent on the present invention proposed a needle selector configured to enable a plurality of fingers to be swung by an attractive or repulsive force of an electromagnet (see Japanese Patent Laid-Open No. 60-224845), which is both faster and more compact than conventional needle selectors and moreover can save electric power consumption. Further, the same applicant as that for patent on the present invention proposed a piezoelectric needle selector which causes knitting needles to be selected by operating the fingers themselves by the bending of piezoelectric bodies in place of the above-cited electromagnetic needle selector (see Japanese Patent Laid-Open No. 62-28451), which achieved further advances in speed increase, size reduction and energy saving for needle selectors.
The same applicant as that for patent on the present invention further invented an improved version of the aforementioned piezoelectric needle selector, and filed on Oct. 5, 1988 the Japanese Patent Application No. 63-249967 for that invention, entitled "Needle Selector for Knitting Machines." This was registered as the Japanese Patent No. 1969970, and the corresponding U.S. patent application was registered as U.S. Pat. No. 5,027,619.
This improved piezoelectric needle selector is illustrated in FIG. 7A. To describe this improved version on the basis of claim 1 of Japanese Patent No. 1969970 with reference to FIG. 7A, this is a knitting needle selector in which fingers 9 are arranged to be movable relative to piezoelectric bodies 7 each having a piezoelectric element; electric power is applied to the piezoelectric elements to actuate the fingers 9; this motion of the fingers 9 causes knitting needles of the knitting machine to be selected (via needle selection jacks); and knitting of a fabric of a prescribed pattern texture is made possible. The rear end of each piezoelectric body 7 is characterized by being movably supported via a spherical body, i.e. a rotary body 20, by a support 21 or a concave part 22 of a housing; the tip of the piezoelectric body 7 is characterized by being movably linked via a spherical body, i.e. a rotary body 16, into a U-shaped groove 17 at the rear end of the finger 9; a prescribed position between the rear end and the tip of the piezoelectric body 7 is characterized by being pinched by a rotary body 23 rotatably fitted to a support 34 or the housing, and the finger 9 and the piezoelectric body 7 are characterized by being arranged on a straight line.
The finger 9, as illustrated in FIG. 7A, its intermediate part is borne by a support 10b through a pin 8, and this arrangement causes any flexion of the piezoelectric body 9 to move the rear end 9a of the finger 9 up and down with the result that the tip 9b of the finger 9 projecting through the opening 11 of the support 10a is thereby moved up and down and this vertical motion causes the rising motion of the knitting needle 2 to be selected.
The bearing of the piezoelectric body 7 movably in a prescribed position enables the piezoelectric body to freely bend, resulting in a significant increase in the acting speed of the finger 9 and moreover, as it was found, an increase in the shifting quantity of the tip of the finger 9. Furthermore, the use of the piezoelectric body in such a configuration serves to reduce damage to the piezoelectric body and thereby to elongate the useful life of the needle selector.
Therefore, this improved piezoelectric needle selector, as its finger actuating device to swing the finger member is innovatively improved, represents a significant enhancement in needle selecting capability, but the electric power supply means to feed power to the finger actuating device in the needle selector is substantially of the same performance standard as any conventional means. Thus, as shown in FIG. 7B illustrating the overall configuration of the aforementioned improved piezoelectric needle selector, in order to supply electric power to the piezoelectric body 7, electrodes 25 should be provided on the surface of the piezoelectric body 7, and these electrodes 25 are connected by wires 27 to connectors 26 of a connector supporting board B. Though wire connection is a very simple structure, at least two wires 27 are needed per piezoelectric body 7, and moreover wire connection of two electrodes requires a space of a certain size, resulting in large hardware dimensions, the risk of accidental wire disconnection and a high cost of wire fitting. Therefore, this configuration lags behind the remarkable performance improvement of the finger actuating device, and has obstructed further size reduction of needle selectors for knitting machines.
An object of the present invention is to solve the above-noted problems preventing the overall performance improvement and size reduction of needle selectors for knitting machines, as a result of the lag of improvement of power supply means behind the improvement of the finger actuating device itself in known such selectors according to the prior art, and accordingly to provide a needle selector for knitting machines, which is improved in performance and reduced in dimensions.